


Inevitable

by Fanhag102



Series: They Don't Last [2]
Category: Life with Derek
Genre: Angst, F/M, Porn With Plot, Porn with Feelings
Language: English
Status: Completed
Published: 2019-05-23
Updated: 2019-05-23
Packaged: 2020-03-13 03:38:47
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,178
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18932641
Author URL: https://archiveofourown.org/users/Fanhag102/pseuds/Fanhag102
Summary: They don't last a day back home.





	Inevitable

“There’s got to be rules,” she says, nodding to herself. He rolls his eyes, predictably, at her, but she has had years of practice ignoring him. 

She’s driving them this time, because she has way too much nervous energy to sit in the passenger seat for two hours, and she thinks better when shes doing something else. And she has a lot she needs to think about. 

She glances over at _him_ in the passenger seat, already kicked back and stretched comfortably, eyes a little heavy like he might be considering a nap. She doesn’t blame him. They were busy with finals practically until the second they left, and his new band that he’d joined mid-semester had a surprise gig the night before. She should probably let him get some sleep. He could definitely use it. But then… she would be left alone in the car with her thoughts and that was _not_ good. 

Because she was panicking, a little. A lot. 

Another glance _his_ way, and this time he catches her. He sighs. 

“Okay, fine,” he says. “What kind of rules?” 

She frowns, staring ahead at the road stretched out in front of them. She’s trying to remember where shes supposed to be driving while also trying _not_ to remember where they’re actually going. 

_Home._

“God,” she says, biting her lip. “We should just stay on campus for Christmas. I don’t think I can do this.” 

“Casey,” he tries to sound soothing, like how you talk to a wild animal. “It’s going to be fine. You’re freaking out for no reason. Just—just tell me about these stupid rules. You’ll feel better if you’re busy trying to tell me what to do.” 

She smiles, but it’s a tight sort of anxious grimace. He puts his hand on her thigh and her grip on the wheel tightens. 

_Why is it_ him? Of all the boys in the world, all the boys in the SCHOOL, why would she fall in love with her step brother? 

It shouldn’t have mattered that they were away from their family, at college, where everything felt so different but everything between them just felt the same. 

Because she won't deny it, she knew she was attracted to him even before college. There were so many heavy moments between them and little electric touches that she brushed off as random or innocuous, but she always knew what they were. She didn’t let herself think about it. They _lived_ together. They were _siblings_. She blocked it out, shut it down, closed it up in the dusty attic of her mind, only to let it out _their first week_ away from home. She was so stupid to think they could ignore it forever. 

She was so stupid to not think about how horrible it would be to go home after they had slept together.

“We can’t tell anyone,” she says finally, with a rushed exhale. “That’s rule number one.” 

“Duh,” he replies with another rolled eye. 

“Our friends, either,” she adds. 

“Okay,” he agrees, but already sounds reluctant. 

“What?” She snaps, sensing an argument. 

“Okay, just hear me out.”

“I don’t want to.” 

“Casey, give me some credit. I know we can’t tell anyone _now_ , I just want to know how long you think we need to keep it a secret. Like, are we talking a year? Until we finish college? Forever?” 

Her heart does a little flutter when she thinks about being with him _forever_. It’s so much to think about when they’ve only been together one semester of school, but she still wants it. She wants it more than she’s wanted any other relationship to last forever. She hopes he can’t tell what she’s thinking. Then _he’d_ be the one freaking out. 

“Probably forever,” she tells him, and his eyes might really roll out of his head. 

“Seriously, Spacey.” 

“Oh, god, I don’t know! There’s no protocol for this! I don’t have any books to reference!” 

He snorts. 

“ _How To Tell Your Parents You Fucked Your Step-Sister: a step by step guide!”_

She groans. 

“I can’t deal with this. It’s a problem for later-Casey. I’m not going to worry about it anymore. Listen, rule number two: no touching.” 

“Oh come on. I’m not an idiot, Case. Do you think Im’ just gonna walk up to you in front of George and Nora and plant a wet one right on the mouth?”

“I’m not worried about that. Well, I am a little now that you said it, because I’m freaking out, but no. I just mean, no casual touching. None of this.” 

She motions to his hand on her leg. He quickly removes it and she immediately misses it being there, warm and constant and weirdly reassuring. 

“We’ve gotten used to being,” she struggles to find the wording, “ _casually touchy_ and I think it might be harder than you expect to switch back to how we were before.”

“Got it,” he sighs. “I know. You’re right. Shit, this is gonna suck. What if we know for sure no one’s looking?” 

She smiles softly despite herself and shakes her head. 

“No touching, Derek. We have to be careful. If anyone finds out they would be really upset.” 

“Marti wouldn’t.”

“That’s because she wouldn’t understand what it meant.” 

“Sure she would, she’s a smarty. She just wouldn’t care.”

“That doesn’t mean we should tell her, Derek.” 

“I know, I know. I’m just saying. When we do eventually tell them… we’ll have at least one person on our side.” 

He doesn’t sound scared at all. She wishes she could be more like him, so confident that everything will just work out. _When we do eventually tell them_. Her heart gives another hopeful, giddy leap. She concentrates on the road.

“Rule three: No sex.” 

“Okay, I think I have an argument for—“

“ _Der_ ek! No sex!” 

____________________________

“We’re home!” He calls into the door, and Marti is the first to appear, fast as lightning, wrapping herself around Derek’s knees. Casey has to smile, even though she feels guilty as soon as she steps into the house. 

The rest of the family appears a moment after, and the hugs go around, and Casey tries to keep calm, to not let it show on her face. 

_They can tell, they can tell, they can tell!!_ Her brain screams at her, helpfully. Lizzie looks at her weird.

“Huh?” She asks, suddenly aware that her sister asked her a question. 

“I said, did you bring us anything?” 

“Yes,” Derek answers for her, “my homework. Make sure to split it evenly between you and Edwin. Have to be fair, after all.” 

Casey kind of stares around at the living room. Did it always feel this small? Did her family always look at her like she was acting suspicious? _Was_ she acting suspicious? 

George is smiling at her. She swallows and tries to smile back like she doesn’t feel like a horrible traitor. 

“Glad to see you two didn’t murder each other,” he says, gruffly hugging Derek with one arm. 

“Do you two see each other a lot at school?” Her mother asks. “You didn’t say whether you had any of the same classes or not.” 

They do, actually, have one class together. Psychology. They always meet up before and make out in Derek’s dorm. They walk to class together holding hands. 

Casey’s mouth feels dry. She catches Derek’s gaze from behind his father’s shoulder and he’s giving her a look. A _Jesus, Space Case, pull it together or you’re gonna screw this up for everyone,_ face. She clears her throat. 

“W—we—yeah, we—“ 

“Casey studied too hard for her finals and her brain fell out of her ears. I swear I saw some brain goop dripping onto her shoulders on the drive here.” He says, bending down to grip Marti’s head and make pretend brain goop drip out of her ears. She giggles and Casey finally pulls it together. She should probably be grateful for the drama class she took for fun.

“That drive is so long!” She says, plastering a smile on her face. “I’ll remember how to function like a person in a minute, guys. I missed everyone so much! When’s dinner? I wanna hear what’s been going on!” 

Everyone accept this easily and they all file further into the house, Lizzie, Edwin, and Marti all talking over each other to tell Casey and Derek what their semesters had been like. Casey breathes deep. She can do this. No one thinks anything is weird. Everything is normal. 

She catches Derek’s gaze on her, subtly, and her stomach tightens. There’s something pinched and _wrong_ about the way he looks at her, and as soon as he notices her eyes on him he looks quickly away and grins at something Edwin said. 

They should have stayed at school over the break. 

_______________________________

He breaks rule number two after dinner. 

She’s in the kitchen doing dishes. She’d volunteered, still wanting something to do with her hands so she didn’t keep thinking about how she was lying to her family. 

“Casey,” his voice is close behind her, his hand on her arm. She can’t remember what’s normal and what’s too casual but she glances at the doorway of the kitchen and he lets go of her but doesn’t move further away. 

“I’m sorry I freaked out,” she whispers, turning the water on to cover their voices. “I’ll be okay.” 

“No,” he sighs, running a hand through his hair. He looks older, somehow. Maybe it’s just seeing him in their kitchen again, like she always used to _before_ college. Before she knew what his face looked like right before he came. 

“This is my fault. I should have known this was…” he trails off and she doesn’t know what he’s about to say, but she does know, too. A vice grip tightens around her heart. 

“Derek,” she says, lets his name hang in the air between them along with everything unsaid. 

“I wasn’t thinking with my head,” he says. “I’m an idiot. I’m a stupid _guy_. I was thinking with my dick. I should have seen how…” He exhales and Casey realizes she hadn’t been breathing. She takes air in and it rattles her chest. He looks at her face, eyebrows creased with concern and apology.

“I should have known this would be harder for you,” he says. “Because I’m me, but you’re… you. J—just don’t worry about it anymore, okay? I’ll try my best to stay away from you while were home, and when we get back to school…” He trails off and looks away, jaw clenched, expression resolute. Casey hates that he looks so handsome when he’s breaking her heart in two. 

What a mess this all is. 

“Just don’t worry about it anymore,” he finishes lamely, and then he turns to go, but not before letting his fingers graze feather-light against her arm. He leaves goosebumps and tears in his wake. 

____________________________________

When they were almost home he’d gestured to a rest stop and told her to get off at the exit. She figured he had to pee, but when she put the car in park he grabbed her face and pulled her to him, grinning sly against her mouth. And she had smiled too, and crawled over the center and onto his lap, hands fisting into his hair (it was getting long again). She chastised him for making them stop so close to home while moaning against the kisses he was pressing into the side of her neck. She pulled his shirt collar down as far as it would go, stretching the cotton so she could suck a mark into his skin where no one would see. His fingers slipped under her shirt and under her bra and then scraped down her back when she rolled her hips over him. 

He asked her if she was getting wet and she chastised him for being lewd, too. He laughed and it turned into a moan when she slipped a hand into his pants. 

“ _Casey,_ ” he said her name like a prayer. 

“ _Casey_.” 

She can't believe that it’s still the same day. Everything is different, and more terrible, now than it had been just a few hours before. And it was all her fault. 

Casey and her worry. Casey and her anxiety and her fear and her fretting. She always has to be the good one, the one who won’t do anything that would upset anyone else, the one who wont break any of the rules. 

Maybe that was why everything was so different at college, that she let herself have something she wanted for once, and didn’t talk herself out of it because it was wrong or someone else wouldn’t like it. She likes the Casey she is at college, and she likes the Casey that she is when she’s with him. 

All of her fretting and all of her careful rules just make her miserable, but _he_ makes her smile, and laugh, and when they were at the rest stop she wasn’t worried about anything—not their parents, or their siblings, or their friends, just his skin against hers. 

Sometimes she can be a real idiot. 

She peeks out of her room carefully even though she knows it’s too late for any of the younger kids to still be awake, and George and Nora were on another floor. They wouldn’t hear her. She goes to his room, placing a hand on the wood and another on the cold doorknob. She can still feel the ghost of his touch earlier and it gives her the courage to open the door. 

He looks up like he’d been waiting for her, but his expression is unsure. She closes the door behind her before she speaks, softly.

“I don’t care about the rules.” 

He sighs heavy, his expression a mix of exasperated and fond. 

“Yes you do.” 

She tiptoes carefully to his bed, the thrill of being in his room in their house with everyone else blissfully unaware of them surges through her. Why had she spent so long worrying when she could have been anticipating? She climbs onto his bed and he winces when it squeaks noisily, but she doesn’t. His hands hover over her hips, eyes uncertain but so, so hopeful. 

“I don’t,” she says, and he gives in, his smile crashing across his face like an avalanche. It should be loud enough to wake the whole world, but it’s just for her. 

He slips his hands beneath her sleep shirt and over her head in one swift motion, his mouth on one of her nipples in the next. She gasps and covers her mouth with her hand. With her breast still in his mouth he looks up at her with bright, _wanting_ eyes. 

She loves him, but that is a secret she doesn’t mind keeping for just a little while longer. 

His tongue licks circles around her nipples. They’re hard and pointed, an obvious sign of her intentions. The tent in his boxers is the obvious sign of his. 

She pulls him up from her breasts to kiss him again, furious and sloppy, stopping only to catch their breaths when he pulls his shirt over his head and throws it on the floor beside hers. She’s rubbing him through his boxers, breasts pushed up against his chest, softly moaning his name. 

He sucks in a breath and gently pushes her back with one hand. She blinks at him and then blushes, contrite. She never knew she could be so eager and needy before him. She didn’t know a lot of things about her body before him. She can feel heat pulsing between her legs and he looks at her, and then, without making barely any noise, flips them over and places himself between her open legs. 

She swallows as he carefully shimmies her underwear down her legs. He leaves them dangling on the end of one of her feet as he presses kisses slowly up the inside of her thighs. His tongue dips out to taste her skin and make her shiver with the anticipation of what’s to come. He pauses when he’s reached the source of the pulsing heat that’s coursing through her body and looks up at her. 

“Don’t scream,” he says. 

She blushes even harder than she already was and covers her mouth with her hand, letting her head fall back on his pillow. _It smells like him_ , she thinks, and then she cant think anymore. 

She bites into the meat of her hand to keep from crying out when his tongue licks lightly into her. He’s gentle, at first, experimental, cautious. But once he’s sure she isn’t going to let herself scream and wake the whole house, he throws caution to the wind. He wants to work every ounce of tension from her body, make every worry vanish from her mind without a trace, and he does it. 

He never cared much about going down on girls before Casey, but she made him love it. Sometimes he likes it even more than sex. _Sometimes._

He likes the noises she makes. 

No. He doesn’t like them. He loves them. 

And somehow, even though shes trying so hard to keep quiet and her hand is covering her mouth, he can still hear them. It urges him faster, and he’s rewarded by her legs squeezing around the sides of his head. She pushes herself harder against his tongue. She tastes so good.

He loves her. But he can’t really tell her that now. 

Casey arches off the mattress and his tongue follows her movement, never letting up his pace. Her whole body is tensed, tensed, tensed, right on the edge, almost ready to—

“Der- _ek,_ ” she gasps, and doesn’t worry about the sound of it until her legs stop shaking and her heart slows and her mind comes back to her. She slaps a hand over her mouth and sits up in time to see him grinning and wiping his mouth on the back of his hand. He leans over her and kisses her deep. She tastes herself on him. 

“Don’t worry,” he says. “You weren’t too loud. Not like usual, anyway.” 

She slaps his shoulder and wants to hide her face in the pillow, but he catches her lips in another kiss, pressing his erection against her hip. She moans into the kiss, already wanting more. 

He pulls away, almost reluctant, but she watches him, lit by one small lamp on the corner table, as he takes off his boxers and searches a drawer for a condom. She stops him before he puts it on, pulling him closer to her so she can lick a line from the base of his cock to the tip. He curses and she smiles before she swallows him, tongue circling as she sucks in. 

“Stop,” he says, but it sounds like he’s begging. She licks on the underside of his cock once more and he groans and steps back.

“I want to be inside you, Casey,” he says as trembling fingers roll the condom over his cock. He pauses for a second, and then snatches her hips, quick, and pulls her to the edge of the mattress. Her pulse is racing again, and she looks at him, and holds his gaze until he breaks away to line his cock up to her entrance. 

He pushes inside and her breathing stutters, matching his. 

He looks at her again, and then his eyes close when he pushes again until he’s all the way. She clenches around him and his hips shake. She squeezes again. 

He leans his body over hers until their noses are touching, but he doesn’t move. 

“We’re in my bedroom,” he says. “At our house. We’re having sex in my bed when everyone’s asleep.” 

He rocks his hips just slightly and she sees stars. The whole world could just be his voice and his cock and her. 

“I jerked off thinking about you on the other side of that wall, once.”

Her eyes widen and he grins, still rolling his hips deliciously slow. He’s trying to keep his voice steady but she can tell it’s an effort. His hands on her waist are trembling. 

“I felt so guilty about it afterwards I could barely look at you, and I never did it again.” 

He pulls almost all the way out and then pushes in, lifting her hips off the bed. She has to cover her mouth with her hand again. He stills, just for a second, his mouth against her ear. 

“It was the greatest fucking orgasm I’d ever had.” 

And then he fucks into her hard and fast, and its so good she thinks it would maybe be worth it, even if their family caught them. It’s so good she says his name over and over and over, and sometimes he says her name too, and they say them together without even realizing. 

It isn’t their fault things ended up like this, her legs hitched around his waist, his cock fucking inside her at a steady, desperate pace. She thinks it was always bound to end up this way. They were inevitable. 

He bends and wraps his lips around her nipples, one at a time, sucking lightly. Her fingernails scrape across his shoulder blades. She has to remember to stay quiet. She has to remember where she is, and who she is, and who he is, and where they are, and what they’re doing, and so many things that don’t seem important when he casually lifts her body and settles her into his lap, his cock going even deeper inside her. She squeezes tight around him. 

“ _Fuck,_ ” he says through gritted teeth, and she feels him hold his breath and slow the movement of his hips. She moves against him and around him and he looks at her, and it looks a lot like danger. That look on his face really turns her on. 

“You feel so fucking good,” he whispers, like he’s admitting state secrets against his will. He moves again, back to a faster, bruising pace. She gasps and clutches to him, burying her face into his shoulder to stop from crying out. He’s going to drive her crazy. 

“You’re so fucking good, Casey,” he says, and its the sound of her name coming from his lips that does her in. 

She pulls away from him, just a bit, and puts her hands on his chest. He stills and looks at her with a question. She kisses him deep, pushing him down until he’s lying on his back. There’s a second of awkward when she pulls off of him to adjust her position and they both moan—almost too loud. They stop moving and wait to see if they can hear someone coming to catch them, but a moment passes and they don’t. She grips his cock and lines it up to slide inside her.

She doesn’t give him a moment to collect himself, and rolls her hips, fucking herself on his cock. His hands slide up her legs and rest on her hips, holding them tight while she fucks him. She closes her eyes and doesn’t think about anything but the feeling of him inside her, and his hands on her, and then she opens her eyes and looks down to see his eyes on her, too. 

Her heart skips at his expression. No matter how many times they have sex she doesn’t think she’ll ever get over the way he looks at her; like she’s everything. 

“ _Derek_ ,” she pants, breathless, rocking up and down on top of him. The pressure is building in her again, a tense coil in her stomach, and there’s sweat mingling with his and soaking into the sheets. 

“I’m gonna come,” he tells her, jaw clenched. “Don’t stop, don’t stop, _fuck_. Wait.” 

“What?” She asks, stilled by surprise. He drags in a ragged breath and his eyes edge slowly over every dip and curve of her body. He licks his lips. 

“After I come,” he says, low and full of promises, “I’m gonna lick you again, and you’re gonna come even harder than before.” 

A shiver runs up her whole body, and she clenches around him at the same time she starts riding him again, faster, deeper, holding in the gasps and moans she desperately wants to let out. 

He throws his head back, mouth open noiselessly, and she rides him through his orgasm, his hands like vice-grips on her ass. His hips stutter into her and then still, and he takes a gasped breath that sounds a lot like her name, and it’s everything. 

When he says her name like that she wonders how she could ever panic or worry or fret about anything. When he says her name it’s like he isn’t saying her name at all. 

It’s almost like he’s saying, “ _You’re mine, and everything is going to be okay.”_

“ _Derek,”_ she sighs. 

And what she means is, 

_“Okay. I believe you.”_

  
  



End file.
